(a) Technical Field
The present disclosure relates, generally, to a method for measuring the temperature of a motor. More particularly, it relates to a method for measuring the temperature of a motor for a hybrid electric vehicle, which can suitably extend the measurement range of motor temperature within a required measurement range and improve the linearity of a temperature sensor.
(b) Background Art
Gasoline and diesel engines that use fossil fuel can have a number of problems such as environmental contamination due to exhaust gas, global warming due to carbon dioxide, respiratory ailments due to increased ozone, etc. Further, since the amount of fossil fuel left on the earth is limited, it will be exhausted in the near future.
Accordingly, various types of environmentally-friendly electric vehicles, such as a pure electric vehicle (EV) driven by a motor (hereinafter referred to as a drive motor), a hybrid electric vehicle (HEV) driven by an engine and a drive motor, a fuel cell electric vehicle (FCEV) driven by a drive motor which is powered electric power generated by a fuel cell, etc., have been developed.
The electric vehicle includes a drive motor for driving the vehicle, a battery as an energy storage device for supplying electric power to the drive motor, and an inverter for driving the drive motor.
The battery that supplies electric power to the drive motor in the electric vehicle is referred to as a high voltage battery (or main battery), which is distinguished from a low voltage battery (or auxiliary battery) that supplies low power to electronic components, and is repeatedly charged and discharged during running of the vehicle to supply necessary power to the drive motor. The inverter inverts the phase of electric power supplied from the battery according to a control signal suitably applied from a controller to operate the drive motor.
Further, the temperature of a specific component is suitably measured and the measured temperature is used to monitor the current status of the corresponding component and to control its related components and system.
For example, the temperature of the motor is suitably measured by a temperature sensor such that when the temperature is low, an inverter corrects the physical properties in which the output of the motor is suitably reduced, and when the temperature is high, the motor is controlled to prevent dielectric breakdown and deterioration of durability due to the overheat.
The temperature sensors mounted in a hybrid electric vehicle are classified into negative thermal coefficient (NTC) sensors and positive thermal coefficient (PTC) sensors. For example, as shown in FIG. 1, the resistance value of the NTC or PTC sensor is suitably converted into a voltage value by a hardware gain circuit 12 to measure the temperature of the motor.
Here, although the required measurement range of the motor temperature is −40 to 200° C., the entire temperature range required is suitably measured, and the sensor having the circuit linearity is not physically present. Therefore, it is necessary to use two types of sensors such as a temperature sensor having the linearity at a temperature of −40° C. and a temperature sensor having the linearity at a temperature of 200° C.
However, the use of the two types of motor temperature sensors in the hybrid electric vehicle increases the manufacturing cost and the number of components to be replaced in the event of failure.
Further, the motor temperature sensors cannot satisfy the linearity in the entire temperature range required by the vehicle, and thus a specific temperature range is linearized and measured.
Typically, the prevention of dielectric breakdown due to overheat of the motor is more important than the prevention of reduction of output, and therefore, as shown in FIG. 2, the temperature of the motor is suitably measured by a hardware gain circuit with respect to the temperature range of 40 to 200° C.
However, it is difficult to use precise information at both high and low temperatures at the same time, and further the stability and reliability of motor control are suitably reduced due to a deviation of the temperature sensor of the motor at a low temperature.
Further, conventionally, a high precision element is used to overcome the above-described problems, which suitably increases the manufacturing cost and the time and effort required to perform a verification test.
Accordingly, there remains a need in the art for methods of measuring the temperature of a motor for a hybrid electric vehicle.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.